Fig. 4.

Physical properties of the experimental setup and the cellular response. (A) The return loss S₁₁ is strongly frequency-dependent. While for f = f_res, a SAW is resonantly excited, at f = f_ref, only the electric field stimulates the cells. (B) To estimate the SAW-intensity at different power levels P_IN and to characterize the flow profile, an sPIV measurement was performed at a height h = +25 µm above the substrate. The liquid is streaming toward the aperture. The streaming velocity (v_as) was determined at the aperture * and the internal reference **. (C) Power- and location-dependent streaming velocity v = v_as. (D) The small asymmetry of the flow profile has no significant impact on the migration velocities of the opposing cell fronts in E.